RSM-CCD approach for optimization study on effective remediation of lead and cadmium from water using surface-modified water caltrop peel biochar

In the present study, MnO2-loaded KOH-activated biochar material derived from the peel of water caltrop was utilized for the remediation of lead and cadmium from water. MnO2-loaded activated biochar was synthesized using two different concentrations of MnO2 (labelled as Mn(1)aBC and Mn(2)aBC). The prepared adsorbents were characterized using XRD, BET, SEM-EDX, TEM, and FTIR. Determination of surface morphology using different characterization techniques revealed that MnO2-loaded activated biochar possesses high surface area and porous structure. MnO2-loaded KOH-activated biochar displayed greater ability for adsorption than KOH-activated biochar. Mn(1)aBC was found to be most efficient for lead and cadmium remediation. The removal capacity of Mn(1)aBC for lead and cadmium was 116.96 and 102.67 mg/g, respectively. The adsorption procedure followed pseudo-second-order kinetics and langmuir isotherm signifying monolayer chemisorption. Statistical approaches of central composite design (CCD) have been employed to optimize the study parameters for adsorption process. A detail mechanism has been elucidated through CCD plots by fitting the data obtained from the batch analysis of kinetics, isotherm, variation of pH, and dose, which reveals to optimize the parameters for the adsorption process of the lead and cadmium onto the surface of the newly developed biochar to implement the process for the natural water system. According to the RSM plots, the removal efficiency of Mn(1)aBC was observed to increase with increasing pH and time, while it decreased with increasing initial ion concentration. The observation that there was a high correlation between predicted and experimental data demonstrated the model's effectiveness in predicting the optimum conditions for maximum efficiency. The developed adsorbent used for the study is a low-cost and environmentally friendly material derived from the waste caltrop peel abundantly available. It has been designed to effectively target a broad range of initial concentrations of lead and cadmium in water.